I'm still a noob to vendetta, but I think it would be handy to be able to write custom notes about systems, stations, and locations in our character's PDA.

You can write down notes already in PDA > Missions > Mission Notes. You can also add a note to a specific sector in the navmap by hovering over the sector on the map and pressing "a".

I believe you can even copy/paste other peoples notes if they send them to you, by going directly into the VO files. Not sure where you'd put them though. I've never actually done it, but I'm told it is possible.

The notes are saved in the /settings/PlayerName/ directory as system1notes.txt to system30notes.txt, where each text file corresponds to all the notes saved for a given system.

And you can save notes for systems too if you zoom out to the galaxy map and press the 'a' key

Very cool, thanks for the info!